<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        .box{
            overflow: hidden;
            display: flex;
            /* flex-wrap: wrap; */
            margin-left:-20px;
        }
        .box div{
           height:100px;
           /* width:25%; */
           flex:1;
           margin-left:20px;
        }
        .a{
            background-color: aqua;
        }
        .b{
            background-color: red;
        }
        .c{
            background-color: blue;
        }
        .d{
            background-color: green;
        }
    </style>
</head>
<body>
    <div class="box">
        <div class="a"></div>
        <div class="b"></div>
        <div class="c"></div>
        <div class="d"></div>
        <div class="a"></div>
        <div class="b"></div>
    </div>
</body>
</html>